impotency

例句：

1. 1. He was impotent to help her when she needed it most.
   在她最需要帮助的时候，他无能为力。
2. 2. The patient had an impotency due to his age.
   由于年龄的原因，病人患有阳痿。
3. 3. The scientist discovered a new impotency in the treatment of cancer.
   科学家发现了一种新的癌症治疗方法的无效性。